In recent years, electronic apparatuses have been sophisticated and diversified. This market trend is accompanied by an increment of electronic apparatuses equipped with an input device such as an optically transparent touch panel on the front face of a display element such as a liquid crystal display (LCD). A user recognizes and selects, via this input device, texts, marks, or symbols shown on the display element, thereby switching the functions of the electronic apparatus.
In the description hereinafter, position-relating terms such as “top surface”, “underside”, “right side”, and “left side” are used. Those terms express a relative relation about positions of elements or sections when the drawings are viewed from the front, and they do not indicate an absolute relation about the positions.
In the description hereinafter, phrases such as “a first principal surface”, and “a second principal surface” are used. The “first principal face” does not always mean a front face of elements such as a wiring substrate, and the “second principal surface” does not always mean a back face thereof In other words, an opposite side of the first principal surface is the second principal surface.
A conventional input device is described hereinafter with reference to FIG. 7–FIG. 9.
FIG. 7 shows a perspective view of a conventional optically transparent touch panel(hereinafter referred to as touch panel), and FIG. 8 shows a perspective view of an essential part of a wiring substrate employed in the touch panel shown in FIG. 1. The upper panel 1 is made from polyethylene terephthalate or polycarbonate film. Optically transparent upper panel 1 has optically transparent upper conductive layer 2 on its whole surface or a selective surface area. Conductive layer 2 is made from indium oxide or tin oxide, and formed on the surface by spattering.
A pair of upper electrodes 3, 4 formed by printing paste such as silver or carbon on upper panel 1 at which the base of upper conductive layer 2 is exposed in a given pattern by etching or laser-cutting. A pair of leaders 3A, 4A are prepared at the ends of upper electrodes 3, 4 respectively.
Lower panel 5 made from glass, acrylic, or poly-carbonate resin includes lower conductive layer 6 of optically transparent and similar to upper conductive layer 2 on its entire area of a principle surface or a selective area thereof. A pair of lower electrodes 7, 8 are formed on lower panel 5 from which lower electrode layer 6 has been removed.
Lower electrodes 7, 8 have a pair of lower leaders 7A, 8A at their ends respectively. Lower conductive layer 6 has plural dot-spacers (not shown) at its given places for maintaining a given space between upper conductive layer 2 and lower conductive layer 6. The dot spacers are formed at given intervals and made from insulating resin such as epoxy or silicon.
Upper and lower panels 1 and 2 are bonded at their circumferences with frame-like spacer 9 having adhesive applied to its upper and lower faces so that upper and lower conductive layers 2, 6 can oppose to each other with a given space maintained. Between the leaders of upper and lower panels 1 and 5, flexible wiring substrate 10, having plural wiring patterns and connectors formed on both the surfaces of substrate 10, is inserted to be held.
As shown in FIG. 8, wiring substrate 10 has a narrower section and a wider section. On a first principal surface of the narrower section, plural wiring patterns 12, 13, 14 and 15 are formed, and on the wider section of substrate 10, connectors 12A, 13A, 14B and 15B are formed independently. Wiring patterns 12 and 13 are coupled to connectors 12A and 13A respectively at their ends.
Wiring patterns 14 and 15 are coupled to wiring patterns formed on a second principal surface of wiring substrate 10 via through-holes 14A, 15A filled with conductive agent. Connectors 14B, 15B are formed on a wider section of the second principal surface independently.
FIG. 9 shows a sectional view of wiring substrate 10. Anisotropic conductive agent 11 is applied on the leaders of upper and lower panels 1, 5 as well as respective connectors of substrate 10, and upper leaders 3A, 4A are coupled to connectors 12A, 13A of the first principal surface of substrate 10 respectively. Lower leaders 7A, 8A of lower panel 5 are respectively coupled to connectors 14B, 15B disposed on the second principal surface of substrate 10. The conventional optically transparent touch panel is thus formed.
In the foregoing construction, an optically transparent touch panel is mounted on the front face of the display element such as an LCD, and each one of the wiring patterns of wiring substrate 10 is coupled to a detecting circuit (not shown) of an electronic apparatus by connectors. The upper face of upper panel 1, namely, the operation panel, is depressed by a finger or a pen, thereby bowing upper panel 1, and the depressed section of upper conductive layer 2 is brought into contact with lower conductive layer 6. The detecting circuit (not shown) applies voltage across upper electrodes 3, 4 as well as lower electrodes 7, 8, for detecting a resistance ratio of those electrodes, so that the position depressed is detected, and a function of the electronic apparatus can be switched to another function.
However, the conventional wiring substrate and the input device employing the same substrate have required double-sided wiring patterns and through-holes, so that the construction of the wiring substrate becomes complicated, which is accompanied by an increment of the number of manufacturing steps. As a result, the input device is obliged to be expensive.
Prior art of the present invention is disclosed in Japanese Patent Unexamined Publication No. 2003-108302. U.S. Pat. No. 6,304,251 also discloses a flat cable similar to the present invention shown in FIGS. 6 and 7.